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2006 自然科学の英語 -ENS-L6
Agricultural ecosystems - productivityL6
English in Natural Science
自然科学の英語
2006 自然科学の英語 -ENS-L6
Ecology applied to agriculture• Aims
– To obtain the optimum yield– To achieve sustainable production
• Natural resources are limited• Ecosystems are NOT stationary
– Climate changes– Nutrient availability– Other: diseases, pests, weeds, predators, etc
• We are not alone: the Earth is not only for us– live in harmony with other creatures that share our planet– be able to cover our needs (food, clothing)– respect and let the rest of the natural world LIVE as well
• Humans = superpredators
2006 自然科学の英語 -ENS-L6
Production systems• Agriculture
– Cultivation• Cereals (grain): rice, wheat, corn, barley, millet• Vegetables: soybean, potatoes, all green vegetables• Fruit: many kinds (trees)• Fibre: cotton, hemp
– Livestock• Grazing: cattle, sheep, goats AND wool, leather• Farm: dairy products, pigs, chicken
– Aquaculture: farming of fish (carp, trout, etc)
• Harvesting of natural ecosystems– Fisheries
• Fish• Shellfish• Whales
– Forests: timber, paper, natural products (resin, rubber)
2006 自然科学の英語 -ENS-L6
Minimizing water losses• Number of stomata/leaf• Stomatal rythms (CAM)• Structural (hair,
cuticule)• Leaf shape• Water gradient (C4)
Factors in agricultural production• Light• Water• Nutrients
– CO2
– Others• N• P• S• K• Ca• Mg• Fe• Trace
elements
Limiting factors
Photosynthesis
CO2 intake H2O transpired
• C3 metabolism– CO2 fixed in phosphoglyceric
acid
• C4 metabolism– CO2 fixed in malic + aspartic
acids
• CAM metabolism– Dark-fixed CO2 (malic acid)– C3 diurnal metabolism
2006 自然科学の英語 -ENS-L6
‘A given area of land can produce up to a certain limit’
• Limiting factors– Land availability– Physiological constraints– Environmental factors
• Light• Temperature• Water• Soil nutrients
– Pests and diseases
Productivity of agriculture
Green Revolution
Genetic improvement
Irrigation
Fertilizers
Chemical control
2006 自然科学の英語 -ENS-L6
Agricultural land (m ha)
• Requirements:– Good soil (nutrients)– Appropriate climate
• Cropland/person– Reduced from 0.23 ha (1950) to 0.11 ha (2000)
• Threats– Urbanization ‘steals’ arable land: 2.8 m ha/year
• 0.04 ha/person
– Desertification: 9 m ha/year (?)– Car ownership: 400,000 ha/year
• 0.07 ha/car USA, Canada, Australia, Brazil• 0.02 ha/car EU, Japan, China, India
Cropland Grazing Total land
Already used 670 930 1,600
Yearly increase 3 4 7
Yearly losses 0.4 3.7 4.1
Total increase/year
3.4 7.7 11.1
Available 2,500 1,200 3,700
2006 自然科学の英語 -ENS-L6
Physiological constraints• Each species has an upper physiological limit
C4 > C3
• Increases in productivity mainly due to genetic improvement (%)
Cultivated strains >> wild type– Polyploid varieties (wheat, corn)– Less leaf and more grain
• Dwarf wheat (Japan 1900s, Mexico 1950s)
– New strains adapted to temperature, light conditions• Winter wheat• Rice (China, 1700s, Japan 1880, IRRI 1960s)
• Methods– Selection of strains & varieties over centuries– Genetic manipulation
2006 自然科学の英語 -ENS-L6
Light intensity and productivity
Country Yield (tons/ha)
France 6.8
Mexico 5.0
India 2.7
• Constraints to light– Latitude
• long daylight hours during growing period
Temperate > Tropical
– Climate pattern• sunny summer better than
cloudyMediterranean > Monsoon
• Threat– Climate change
• Cloudy pattern UP
Country Yield (tons/ha)
California 5.8
Spain/Australia 5.4
Japan/China 4.5
India 2.0
Wheat yields
Rice yields
2006 自然科学の英語 -ENS-L6
Water and productivityProductivity ∞ soil moisture
1000 L water 1 kg grain
• Rain fed– Grazing land– Crops: wheat, barley
• Irrigated (25-60% efficiency)– Rivers– Groundwater (well)
• Rice, corn• Cotton• Green vegetables
% usage
Irrigation 70
Industry 20
Residential 10
2006 自然科学の英語 -ENS-L6
Water availabilityH2O absorbed by roots by osmosis• Pore size in soil - surface tension (capillarity)• Osmotic pressure - nutrients, salts salination drying wilting waterlogging anaerobic rot
Soil texture
SandyDrain water
LoamyRetain-release water
ClayRetain water
2006 自然科学の英語 -ENS-L6
Are we running out of water?
• Climate changes– More evaporation– More rainfall– Climate re-distribution
• Aquifer depletion– Rechargeable aquifers
rainfall supply ≥ usage– Fossil aquifers
• Great Plains USA• Saudi Arabia• North China Plain
Aquifers Rivers running dry
Afghanistan Amu Darya
China 27% gone Fen
Yellow
Egypt Nile
India
Pakistan
6 m/yr Ganges
Indus
Iran 5 b ton/yr
Israel gone
Mexico 1/3 total
Saudi Arabia 60% gone
USA 24% gone Colorado
Yemen 2 m/yr
2006 自然科学の英語 -ENS-L6
Nutrient availability
• Nutrient content– N fixing micro-organisms
• Legume symbiosis
– Debris recycling• microorganisms• soil fauna
• Soil type – mineral composition
• Rich: volcanic, alluvial• Poor: acidic, sandy, tropical
(washed off)
• Soil structure– Horizons (layers)
• 0 and A rich in nutrients
– Texture• loam, clay, sand
2006 自然科学の英語 -ENS-L6
Soil threats• Exhaustion of nutrients
– Intensive cropping nutrient depletion– Solutions
• Fallow: land put aside to recover fertility• Crop rotation using legumes (N2 fixation) = biofertilizers• Add fertilizers (NH4,urea, super-phosphates)
• Erosion = loss of soil– Agents: wind and water– Causes
• Tillage– plowing unprotected land after cultivation (bare soil)
• Overgrazing by livestock – animals/area > grassland carrying capacity
Ex tillage + Overgrazing erosion desertification
SUSTAINABLE
UNSUSTAINABLE
2006 自然科学の英語 -ENS-L6
Desertification = land degradationsoil loss > soil formation
– Land fertility decreases– Human settlements move out– Dust storms increase contamination
Water Wind Total
Asia 158 153 311
Africa 119 160 279
Europe 48 39 87
Australasia 70 16 86
North America 38 38 76
South America 35 27 62
Total 468 433 901
Soil degradation (m ha) in the world (UNEP 1990)
Number
1950-59 5
1960-69 8
1970-79 13
1980-89 14
1990-99 23
Dust storms in China
2006 自然科学の英語 -ENS-L6
Animal production• Products
– Meat– Skins: leather– Fibre: wool
• Meat efficiencykg grain / kg meat– Beef 7– Pork 3.5– Chicken 2– Fish 1.5
• 37% world grain used in meat production
Annual growth %
Aquaculture 9.7
Poultry 4.9
Pork 2.5
Mutton 1.6
Beef 0.8
Fish catch 0.8
2006 自然科学の英語 -ENS-L6
The human ‘ecological footprint’ (2000)• Area per person: 0.5 ha -- 5 ha (USA)• Grain consumed per person (kg/yr)
200 India -- 400 Italy -- 800 USA
1 person World
Grain 252 kg 14 m tons
Meat 148 kg 8 m tons
Fish 15 kg 1 m tons
Water 520 m3 29 b m3
Land 0.5 ha 35 m ha
Vehicles 0.13 9 m
2006 自然科学の英語 -ENS-L6
Grain production
• Rice & wheat stable for last 10 years
• Corn: still increasing
Rice
Wheat
Corn
Period Yield/ha
(tons)
Annual increase (%)
2000 2.79 1.2
1990 2.47 2.1
1980 2.00 1.9
1970 1.65 2.5
1960 1.29 2.0
1950 1.06
World grain yields (1950-2000) - various sources
2006 自然科学の英語 -ENS-L6
Depletion of resources
• Aquifers in Middle-East (over-exploitation)
• Arable land in China (desertification)
2006 自然科学の英語 -ENS-L6
The Japan syndrome• Development leads to
– Reduced agricultural production– Diversification of food imports– Reduction in women fertility
• Japan, South Korea, Taiwan…China?
Other country’soverproduction
STOCKS
2006 自然科学の英語 -ENS-L6
Current trends
• Increased fish and seafood consumption– 85 m tons/year
(5 x 1950 production)
• Aquaculture– Most efficient way to
produce animal protein– Soya meal production
2006 自然科学の英語 -ENS-L6
Deforestation= squandering
• Soybean Chinese aquaculture
– Brazil– Argentina
• Palm oil bio-fuel, cooking, detergent
– Indonesia– Malaysia products
Developedcountries
Developingcountries
demand
Natural resources
jobs
$ ¥
Free trade ?Irrational usage
2006 自然科学の英語 -ENS-L6 (Krebs, 2001)
Forestry: timber + products• Population dynamics of a forest vs productivity
– Saplings take more than 10-15 years to grow– Mature cohorts are better than old trees
sappling mature old
2006 自然科学の英語 -ENS-L6
Harvesting: maximum yield• Obtained by
keeping a population at one-half the carrying capacity (K)
R + G = M + Y
R = recruitmentG = growthM = natural mortalityY = yield
Ymax = K/2
2006 自然科学の英語 -ENS-L6
Optimum yieldEconomics• Yield = profit ($, ¥)• Aim: maximum profit
– Ymax is too costly
– Optimum yield < Ymax
Ecology• Aim: sustainable yield
– Ymax = K/2
– Optimum yield << K/2• fluctuations in natural
populations
• diseases, etc
Disease
2006 自然科学の英語 -ENS-L6
Depleted fisheriesNorthern cod (Canada Fisheries, 1999)
Souther Hemisphere whales (Allen, 1980)
Red king crab (Alaska Fisheries, 1999)
2006 自然科学の英語 -ENS-L6
References
• Lester R. Brown. 2004. Outgrowing the Earth. W.W. Norton, New York
• Charles J. Krebs. 2001. Ecology / 応用動物昆虫学 B-226
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